Re: GDB 13.1 and clang

John Baldwin
2023-03-08T22:54:24Z

On 3/8/23 1:22 PM, Chris Johns wrote:
> On 9/3/2023 5:22 am, Simon Marchi wrote:
>> On 3/8/23 15:07, Chris Johns wrote:
>>> Hi,
>>>
>>> I have just tried to build the latest RTEMS tools and we now use gdb 13.1. I am
>>> seeing a build failure on FreeBSD 13.1 of:
>>>
>>> In file included from ../../gdb-13.1/gdb/xml-tdesc.c:23:
>>> In file included from ../../gdb-13.1/gdb/target.h:42:
>>> In file included from ../../gdb-13.1/gdb/infrun.h:21:
>>> In file included from ../../gdb-13.1/gdb/gdbthread.h:26:
>>> In file included from ../../gdb-13.1/gdb/breakpoint.h:38:
>>> ../../gdb-13.1/gdb/target/waitstatus.h:113:1: error: use of undeclared
>>> identifier 'DIAGNOSTIC_ERROR_SWITCH'
>>> DIAGNOSTIC_ERROR_SWITCH
>>> ^
>>>
>>> I only have clang installed on the FreeBSD machine.
>>>
>>> A quick review of include/diagnostics.h seems to show support for
>>> DIAGNOSTIC_ERROR_SWITCH only in the gcc area?
>>
>> Hmm, I see it in the clang section:
>>
>> # define DIAGNOSTIC_ERROR_SWITCH \
>> DIAGNOSTIC_ERROR ("-Wswitch")
>>
>
> It seems I need to do a better review before posting :)
>
>> https://sourceware.org/cgit/binutils-gdb/tree/include/diagnostics.h?h=gdb-13.1-release&id=4f3e26ac6ee31f7bc4b04abd8bdb944e7f1fc5d2#n76
>>
>> Unless there's a typo I don't see.
>>
>> diagnostics.h is included at the top of waitstatus.h. Is it possible
>> that another unrelated diagnostics.h gets included on FreeBSD? You
>> could inspect the preprocessed file to see what the preprocessor
>> included for diagnostics.h.
>
> There is another version installed here:
>
> $ pkg which /usr/local/include/diagnostics.h
> /usr/local/include/diagnostics.h was installed by package binutils-2.37_2,1
>
> We have /usr/local/include early in the include list on FreeBSD to pick up some
> of the required libraries installed as packages. I will check for a package
> update or I revisit the build flags to see how it can be handled.
>
> Thank you for the prompt and helpful responses.

Yes, I manually delete all the headers installed by binutils into
/usr/local/include when building GDB from source locally to work
around this. :( I'm not sure of the best fix for this. I tracked
it down to the change to add zstd as ZSTD_CFLAGS is before BFD_CFLAGS
in INTERNAL_CFLAGS_BASE in Makefile.in in this commit:

commit 2cac01e3ffff74898c54fa5e6418817f5578adb6
Author: Fangrui Song <maskray@google.com>
Date: Mon Sep 26 19:50:13 2022 -0700

binutils, gdb: support zstd compressed debug sections

PR29397 PR29563: Add new configure option --with-zstd which defaults to
auto. If pkgconfig/libzstd.pc is found, define HAVE_ZSTD and support
zstd compressed debug sections for most tools.

* bfd: for addr2line, objdump --dwarf, gdb, etc
* gas: support --compress-debug-sections=zstd
* ld: support ELFCOMPRESS_ZSTD input and --compress-debug-sections=zstd
* objcopy: support ELFCOMPRESS_ZSTD input for
--decompress-debug-sections and --compress-debug-sections=zstd
* gdb: support ELFCOMPRESS_ZSTD input. The bfd change references zstd
symbols, so gdb has to link against -lzstd in this patch.

If zstd is not supported, ELFCOMPRESS_ZSTD input triggers an error. We
can avoid HAVE_ZSTD if binutils-gdb imports zstd/ like zlib/, but this
is too heavyweight, so don't do it for now.

```
% ld/ld-new a.o
ld/ld-new: a.o: section .debug_abbrev is compressed with zstd, but BFD is not built with zstd support
...

% ld/ld-new a.o --compress-debug-sections=zstd
ld/ld-new: --compress-debug-sections=zstd: ld is not built with zstd support

% binutils/objcopy --compress-debug-sections=zstd a.o b.o
binutils/objcopy: --compress-debug-sections=zstd: binutils is not built with zstd support

% binutils/objcopy b.o --decompress-debug-sections
binutils/objcopy: zstd.o: section .debug_abbrev is compressed with zstd, but BFD is not built with zstd support
...
```

I have not tried moving ZSTD_CFLAGS after BFD_CFLAGS, but if it worked I
think the right solution is to ensure all the "local" includes for things
in git come first before any includes that pull from the installed system.
I think this would mean moving READLINE_CFLAGS (for systems that use a
system readline), ZLIBINC, and ZSTD_CFLAGS after INCLUDE_CFLAGS.

I just tried this and it worked for me locally:

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 6e39383eb93..40497541880 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -629,8 +629,8 @@ INTERNAL_CPPFLAGS = $(CPPFLAGS) @GUILE_CPPFLAGS@ @PYTHON_CPPFLAGS@ \
# INTERNAL_CFLAGS is the aggregate of all other *CFLAGS macros.
INTERNAL_CFLAGS_BASE = \
$(GLOBAL_CFLAGS) $(PROFILE_CFLAGS) \
- $(GDB_CFLAGS) $(OPCODES_CFLAGS) $(READLINE_CFLAGS) $(ZLIBINC) \
- $(ZSTD_CFLAGS) $(BFD_CFLAGS) $(INCLUDE_CFLAGS) $(LIBDECNUMBER_CFLAGS) \
+ $(GDB_CFLAGS) $(OPCODES_CFLAGS) $(BFD_CFLAGS) $(INCLUDE_CFLAGS) \
+ $(READLINE_CFLAGS) $(ZLIBINC) $(ZSTD_CFLAGS) $(LIBDECNUMBER_CFLAGS) \
$(INTL_CFLAGS) $(INCGNU) $(INCSUPPORT) $(LIBBACKTRACE_INC) \
$(ENABLE_CFLAGS) $(INTERNAL_CPPFLAGS) $(SRCHIGH_CFLAGS) \
$(TOP_CFLAGS) $(PTHREAD_CFLAGS) $(DEBUGINFOD_CFLAGS) $(GMPINC) \

--
John Baldwin